1. Field of the Invention
This invention relates, generally, to pipeline surface preparation systems. More particularly, it relates to machines that travel along the length of a pipeline and remove coating therefrom by the application of water jets at ultra high pressure.
2. Description of the Prior Art
The disclosure made in U.S. Pat. No. 5,238,331 to Chapman is believed to be relevant to the present invention because it describes a pipeline surface preparation system that is sufficiently light-in-weight to enable a team of two workers to place it into position around a pipeline in the absence of weight-lifting machinery. A frame surrounds the pipeline and said frame supports wheels that engage the surface of the pipeline and enable the pipeline surface preparation system to travel along the extent thereof. Moreover, the Chapman apparatus employs water jets to strip coating from a pipeline. Water nozzles are circumferentially spaced about the perimeter of the pipeline and limit switches are employed to cause the frame that carries the nozzles to reciprocate along a circumferential path of travel so that hoses connected to the apparatus are not wrapped around the pipeline as the apparatus advances along the length thereof.
The invention disclosed in said patent therefore solves several problems left unsolved by earlier advances in the field. Earlier devices are so heavy that a crane is needed to lower them into position atop a pipe. The weight of such devices causes the pipe to sag and thus limits the length of pipeline that can be excavated at any one time. When a crane drops one of the early heavy pipeline surface preparation systems onto a pipeline, catastrophic explosions may occur.
However, the art has not heretofore solved all of the outstanding problems associated with pipeline surface preparation systems. One of the outstanding, unsolved problems relates to handling of debris generated by the pipe coating removal process. Old coating commonly includes asbestos and other materials that require special handling. However, the pipeline surface preparation systems of the prior art do not adequately address the debris-handling problem. The conventional wisdom is that Visqueen(copyright) plastic or other suitable sheet material should be placed in overlying relation to the ground below the pipeline undergoing reconditioning. Asbestos and other debris is thus collected atop the plastic sheet material as the machine travels along the extent of the pipeline. Workers then carefully fold the plastic sheet material in an attempt to contain the hazardous materials deposited thereatop. The inadequacies of this well-known procedure are readily apparent. Asbestos in small pieces may easily float in the air beyond the reaches of the plastic sheet material and enter the lungs of workers in the vicinity. Asbestos may also enter the lungs of those who attempt to collect it by folding the plastic sheet material into a collection means.
A pipeline surface preparation system that prevents asbestos and other hazardous debris from escaping into the atmosphere and that minimizes total contaminated waste is clearly needed.
The earlier pipeline surface preparation systems also slip from time to time as they travel along a pipe because insufficient engagement is provided between the pipe surface and the rollers or wheels that rotatably engage said surface to cause the pipeline surface preparation system to travel along the pipe. When a pipeline surface preparation system slips, the pipeline can be damaged because the water jets have extended dwell time on the surface. It is very important that the extremely high pressure water jets that are used to strip away pipe coating be applied to the surface with controlled speed and rotation. When a pipeline surface preparation system carrier means slips, exposed pipe is subjected to the full power of the high pressure water jets for an extended time and pipeline damage may occur. A pipeline surface preparation system having improved traction is therefore needed.
A closely related problem is known in the industry as the xe2x80x9chot spotsxe2x80x9d problem. A xe2x80x9chot spotxe2x80x9d is a location on a pipe surface that is subjected to more water pressure than other sections. A hot spot is created whenever a nozzle passes closer to the surface of the pipe in one location than it does in another. Thus, a hot spot may be created by slippage of the transported means as just mentioned, or it may be created by the inherent structural features of the pipeline surface preparation system. The prior art includes a nozzle assembly where a pair of nozzles is mounted to opposite ends of a rotating conduit that is straight in configuration. As a result, the nozzles pass closer to the surface of the pipe in some locations than others, giving rise to the problem of hot spots.
A need therefore exists for a structural design that eliminates hot spots by ensuring that all nozzles are spaced equally from the pipe surface at all times.
It is also important to monitor the air supply and the operation of all water-emitting nozzles because any failed movement will direct a high pressure water stream to a single spot and thereby damage the pipe. Automatic monitoring means should therefore be connected to the air supply, each nozzle, and other movable parts. A means should be provided for sending a xe2x80x9cshut-downxe2x80x9d signal to the ultra high pressure system when any required motion fails.
Yet another outstanding problem relates to the debris created by the stripping action of the water jets. The known pipeline surface preparation systems produce debris in large particle size. The art has addressed this problem by providing an external shredding means to reduce the debris particles to a more manageable size. The price of an external shredder increases the cost of the system, the time required to operate the external shredder decreases productivity, and the operation of the shredder could potentially add to environmental concerns with hazardous wastes.
However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the art how the known pipeline surface preparation systems could be improved.
The long-standing but heretofore unfulfilled need for a machine that performs surface preparation of pipelines by stripping coating therefrom is now met by a new, useful, and nonobvious invention.
The novel structure includes a vacuum shroud having a main wall that surrounds a longitudinally-extending section of a pipeline. The vacuum shroud has end walls that are apertured to receive the pipeline. A plurality of equidistantly and circumferentially spaced apart nozzle openings are formed in the main wall and an ultra high pressure water nozzle is positioned within each of the nozzle openings.
A carrier assembly causes the vacuum shroud to travel along the extent of the pipeline in a predetermined direction. An oscillating means oscillates the vacuum shroud in a first rotational direction and in a second rotational direction opposite to the first rotational direction as the vacuum shroud travels along the pipeline.
A vacuum opening is formed in the vacuum shroud at a lowermost end thereof. A vacuum hose has a leading end connected to the vacuum opening and a trailing end adapted to be connected to a remote source of negative pressure. A filter trap disposed between the vacuum opening and the remote source of negative pressure collects debris stripped from the pipeline. Accordingly, debris collected within the filter trap is not discharged into the atmosphere.
The carrier assembly includes a frame having a leading end that circumscribes the pipeline, a trailing end that circumscribes the pipeline, and interconnecting frame members that interconnect the leading end and the trailing end to one another. Stand-off means in the form of a plurality of wheel members that are rotatably mounted to the frame rollingly engage the pipeline and position the frame in concentric, encircling relation thereto.
The carrier assembly further includes a driving wheel assembly that includes a leading drive wheel and a trailing drive wheel that are in line with one another and which rollingly engage the pipeline at longitudinally spaced apart points. The driving wheel assembly surmounts the pipeline.
The main wall of the vacuum shroud has a cylindrical main body and a wedge-shaped lower body formed integrally therewith. The lower body has a lowermost point positioned coincident with a vertical plane that bisects the pipeline when the machine is in a position of equilibrium so that debris created when said coating is stripped from the pipeline falls under the influence of gravity into the wedge-shaped lower body.
Each of the nozzle openings is formed in the cylindrical main body so that each high pressure water nozzle is spaced a common distance from the pipeline so that hot spots are not created when the machine is in operation.
An automatic motion sensing system sends a signal to a shut-down control system to immediately deactivate the machine when a motion failure is electronically detected.
A closed loop filtration system filters and recycles liquid used in a cleaning process of the machine.
An important object of the invention is to provide a pipeline surface preparation system that substantially prevents hazardous materials from entering the atmosphere and minimizes waste to be disposed of during a pipe reconditioning process.
Another important object is to provide a carrier means that provides an increased amount of traction between the surface of the pipeline and the wheels or rollers that engage said surface.
Still another important object is to provide non-destructive cleaning of a pipeline that eliminates the xe2x80x9chot spotxe2x80x9d problem that has troubled the industry for many years.
Another object is to provide a control means that automatically deactivates the system when any required motion fails so that damage caused by such motion failure may be prevented.
Yet another object is to provide a pipeline surface preparation system that shreds debris into very small particles so that no external shredder means is required.
The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts that will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.